Epilepsy is the second most prevalent neurological disorder, affecting approximately 2 million people in the United States. While many patients achieve satisfactory seizure control with pharmacotherapy, there is a significant proportion (20-40%) who have medically intractable seizures. For these patients identification of novel methods for seizure control is a high priority. One such method may be to harness endogenous seizure suppressive circuits in the brain. Because seizures may have multiple or unknown sites of initiation, focal stimulation approaches (e.g., deep brain stimulation [DBS]) that can control seizures originating in diverse brain networks are highly desirable. The circuitry of the basal ganglia has received particular attention in this regard. Here, we propose to employ optogenetic methodologies to analyze the contribution of the nigrotectal pathway and its descending projections to the pedunculopontine nucleus to seizure control. The SNpr is major source of inhibitory input to DLSC. Moreover, both DLSC and SNpr both provide synaptic input to PPN. In Aim 1, we will test the hypothesis that optogenetic silencing of the SNpr, activation of DLSC, or silencing of SNpr to DLSC projections will control spontaneous recurrent seizures in a post-status epilepticus model. In Aim 2, we will determine if projections from SNpr/DLSC to the PPN are necessary and sufficient to account for basal-ganglia mediated seizure control. We will dissect the contribution of multiple cell types within the PPN, separately analyzing glutamatergic and cholinergic cell groups. In the service of these aims, we will examine the effects of optogenetic manipulations on complementary spontaneous and evoked seizure models to map the contributions of this network to seizure suppression within divergent seizure circuits. Together the proposed studies will provide proof of principle for optogenetic modulation of seizures in diverse networks from a single circuit. Moreover, this approach allows us to examine previously untestable hypotheses about the connections that mediate basal ganglia seizure control. Finally, the proposed experiments aim to uncover the circuit and neurotransmitter mechanism by which focal manipulations in motor control regions (i.e., SNpr/DLSC) translate into brain-wide changes in excitability.